Recovering photos within an App

I had an app that I would use to store photos after editing them, but the developers of the app fell through and abandoned it all together. Since then, I'm unable to log into the app to view my photos. When I check the storage on my phone under settings though, it shows the app is still taking a few gigs worth of space, which to me means the photos still exist. Anyone know of an alternative method for me to transfer the photos onto my computer? I know in the past you could transfer photos from apps via iTunes, but I haven't seen that method anymore.